Method of storing and transporting aluminium alloy coiled products

ABSTRACT

A method of storing and transporting a set of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition, wherein the coils are stored and transported in a housing defining a storage area adapted and configured to receive and store the coils, and wherein the housing is formed by an intermodal container and includes a temperature control unit integrated with the housing operative to control the temperature within the storage area defined by the housing to a temperature in a range of 15° C. or less.

FIELD OF THE INVENTION

The invention relates to a method of storing and transporting a set of multiple coils of 6xxx-series aluminium alloy sheet material.

BACKGROUND OF THE INVENTION

The industrial scale automotive sheet production of the heat-treatable AlMgSi-alloy series, also known as 6XXX- or 6000-series aluminium alloys, comprises several discrete steps, including casting of a rolling ingot, preheating of the rolling ingot for several hours for homogenization of the microstructure, hot rolling into hot rolled strip to intermediate gauge, next the hot rolled strip is cold rolled to final gauge in several passes, and at final gauge, the strip is solution heat treated (SHT) and quenched to adjust the required material properties. The SHT can be done either in a continuous annealing furnace or in a batch type furnace. An economical attractive method of producing 6000-series aluminium sheet material is by means of continuous annealing at final gauge. Near the end of a continuous annealing furnace, the sheet material reaches the solution heat treatment temperature and is subsequently rapidly cooled or quenched. By these processing steps, at least the main alloying elements Mg and Si are mostly dissolved during SHT and retained in solid solution by the quench operation leading to a good formability, control of the yield strength, and bake hardening behaviour. The evolution of the microstructure at ambient (room) temperature brings the sheet material from a W (as quenched) to a T4 condition. When also pre-aged the sheet material is in a T4P condition. In T4 or T4P condition, the sheet material is usually formed during a forming operation (for example, by means of deep-drawing or stamping) into a three-dimensional shaped part or component and is then made part of an assembly of other metal components as is regular in the art for manufacturing vehicle components, and is then subjected to a paint bake operation to cure any paint or lacquer layer applied. After the paint bake operation, the aluminium sheet material achieves its final properties. To obtain an indication of the properties after forming and paint bake cycle and for testing purposes, it is practice in the industry that the material in the T4 or T4P condition is subjected to a simulated forming and paint-bake cycle for the assessment of relevant engineering properties. This includes stretching the material for 2% and holding it at 185° C.@20 minutes; this would bring the sheet material to a T6 condition. For the forming of complex shaped parts, it is important that the aluminium sheet in T4 condition has a high formability which is expressed amongst others by a low tensile yield strength and tensile proof strength and a high elongation (uniform and elongation at fracture). For several aluminium alloys in a T4 condition, these properties are adversely affected over time and may ultimately limit the formability. For many Original Equipment Manufacturers (OEMs), it is important that the formability characteristics remain within a certain narrow range for at least up to 6 months, and this stability of formability characteristics determines the shelve lifetime of the subject aluminium sheet material.

DESCRIPTION OF THE INVENTION

As will be appreciated herein below, except as otherwise indicated, aluminium alloy and temper and condition designations refer to the Aluminium Association designations in Aluminum Standards and Data and the Registration Records, as published by the Aluminium Association in 2016 and are well known to the persons skilled in the art.

The present invention provides a method of storing and transporting a set of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition wherein said coils are stored in a housing formed by an intermodal container defining a storage area adapted and configured to receive and store said coils, and wherein the housing comprises a temperature control unit integrated with said housing and adapted and operative to control the temperature within said storage area defined by said housing to a temperature in a range of 18° C. or less, and preferably in a range of 15° C. or less. More preferably, the temperature is kept in a range of 1° C. to 15° C., and more preferably, of 4° C. to 15° C., and most preferably, from 8° C. to 15° C. The temperature should not drop to or below zero ° C. to avoid any undesirable ice accretion on the coils.

In accordance with the invention, it has been found that when the coils of 6xxx-series aluminium alloy sheet material are kept at a temperature of 18° C. or less, and preferably 15° C. or less, during storing and transportation that the shelve lifetime is significantly increased. The temperatures in a regular industrial manufacturing environment of aluminium sheet material are typically at room temperature (about 20° C.−25° C.) or higher. The storage of produced coils at these temperatures have an adverse effect on the shelve lifetime. Now the required formability characteristics of 6xxx-series aluminium alloy sheet in a T4 or T4P condition remain at an about constant level or at least within a narrow range for more than 6 months and, in the best examples, for more than 12 months. From a time perspective, this makes the logistical handling of such coils of aluminium alloy sheet material less critical. It also enables to create a less critical shelve lifetime contingency plan with an OEM.

The housing has integrated therein a temperature control unit that is preferably positioned to minimize interference with the space within the housing. Such temperature control units are well-known in the art and commercially available.

In an embodiment, the housing further comprises a power source adapted or operative to provide power to the temperature control unit. Preferably, the power source is selected from the group consisting of an electric generator and a battery. The generator may comprise a diesel electric generator.

The internal storage area of the housing is defined by a floor, ceiling, front and rear walls, and opposed side walls. The interior defines a cargo storage area within which the set of coils can be stored, secured and isolated during the duration the same is transported via truck, rail and/or ship from a production facility of the coils aluminium alloy sheet to the automotive OEM.

The housing is formed by an intermodal container; such a container is also known as an ISO container. This relates to a large standardized shipping container, designed and built for intermodal freight transport such that these containers can be used across different modes of transport (ship, rail and truck) without unloading and reloading of the coils. Although the lengths may vary, the length is preferably of 20-foot (6.1 m) or 40-foot (12.2 m) or 45-foot (13.7 m) or 53-foot (16.15 m).

In the storage area of the intermodal container, the individual coils are positioned using appropriate means like bedding beams or cradles. The coil orientation uses the direction of the coils axis and refers to this as the “eye”. The coil orientation can be eye-to-side, eye-to-sky, or eye-to-rear. In a preferred embodiment, the coil orientation is eye-to-sky to prevent or at least to limit any build-up of water.

In an embodiment, the set of multiple coils of 6xxx-series aluminium alloy sheet material has a number of coils in a range of 2 to 20, and preferably 3 to 8, stored in each intermodal container.

In an embodiment, the 6xxx-series aluminium alloy sheet material is made from an alloy selected from one of the AA registered alloys 6005, 6111, 6013, 6014, 6016, 6022, 6056, and modifications thereof.

Since the multiple coils of 6xxx-series aluminium alloy sheet material in the T4 or T4P condition stay considerable time in the defined storage area of the intermodal container, it is important to avoid the build-up of moisture in the storage area, and it is key to prevent the migration of humid air from penetrating an individual coil so as to avoid water condensation.

In an embodiment, the housing within the storage area comprises at least one module of an anti-humidity material which assists in keeping the relative humidity in the storage area low to limit or to avoid any condensation on the coiled aluminium sheet material.

In an embodiment, each individual coil within the set of coils is fully covered with a packaging, preferably with a volatile corrosion inhibitor comprising packaging material, to limit the occurrence of any initiation of corrosion and to limit the risk of staining due to possible condensation on the aluminium sheet material.

Preferably, any packaging, e.g. plastic foil, should be very tightly wrapped around a coil limiting or avoiding any air contained between the aluminium surface of the coil and the packaging. Under certain conditions, such confined air is a potential source of undesired condensation on the aluminium surface of the coil, for example, when bringing the wrapped coil to a cooler environment. The packaging has to be tight to avoid that the aluminium coil is corroded or stained by the condensation which may occur on the external surface of the wrapped coil when the aluminium coil is unloaded or transported from its cooled housing to an area having a higher temperature ambiance, whose dew point is above the coil temperature. One or more moisture indicator labels positioned between the packaging and the aluminium surface of the coil can be used as an indicator for the occurrence of undesirable moisture formation. In a preferred embodiment, the packaging is pulled through the eye of the coil leaving the inner diameter free for handling of said coil by cranes or forklifts and to limit the amount of air entrapped in the packaging.

A coil of industrially produced aluminium sheet has typically an outer diameter in a range of about 1 meters to about 1.6 meters and a width in a range of 0.8 meters to 2.6 meters. Air is trapped between aluminium sheet windings. Unavoidably, air can also be trapped between the aluminium outer-surface of the coil and the packaging. As set out herein the packaging, e.g. plastic foil, should be very tightly wrapped around a coil limiting or avoiding any air contained between the aluminium outer-surface of the coil and the packaging. This means that the amount of air contained between the aluminium outer-surface of the coil and the packaging is less than 10% of the total amount of air contained by the aluminium coil. Preferably, this total amount of air is less than 5%, and more preferably less than 1%.

Preferably, the sides of each coil of aluminium alloy sheet material facing the sheet edges are fully covered with a protective material against abrasion. Such a protective material is preferable capable of absorbing some moisture limiting any condensation having otherwise an opportunity to run off and to penetrate the coil. A very useful protective material is formed by cardboard, optionally further containing a purposive additive to inhibit water staining.

In an embodiment, the set of multiple coils of 6xxx-series aluminium alloy sheet material are stored for at least 30 days, and preferably for at least 60 days, and more preferably for at least 90 days within said housing. The housing provides a temperature stable environment increasing the shelve lifetime of the aluminium coils by about the number of days these remain at the pre-set temperature. The aluminium coils are no longer subjected to temperature differences between day and night or seasonal temperature fluctuations. When the aluminium coils are stored and transported in the intermodal container, temperature fluctuations due to loading and unloading during inter-regional or inter-continental transit are also avoided, and the corresponding chance of condensation on the aluminium coils is reduced or even avoided.

The invention further relates to the use of an intermodal container having a housing defining a storage area adapted and configured to receive and store coils of metal sheet, the housing comprises a temperature control unit integrated with said housing and operative to control the temperature within said storage area to a temperature in a range of 18° C. or less, and preferably of 15° C. or less, for storing and transporting of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition.

The invention further relates to a kit-of-parts formed by a set of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition and an intermodal container having a housing defining a storage area adapted and configured to receive and store said coils, the housing comprises a temperature control unit integrated with said housing and operative to control the temperature within said storage area to a temperature in a range of 18° C. or less, and preferably of 15° C. or less, for storing and transporting said set of multiple coils. Preferred embodiments or features for the intermodal container, storage temperature and time, and the aluminium alloy sheet material and packaging are as herein described and claimed. 

1. A method comprising: storing and transporting a set of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition, wherein said coils are stored and transported in a housing defining a storage area adapted and configured to receive and store said coils, and wherein the housing is formed by an intermodal container and comprises a temperature control unit integrated with said housing and operative to control the temperature within said storage area defined by said housing to a temperature in a range of 18° or less.
 2. The method according to claim 1, wherein the housing further comprises a power source operative to provide power to said temperature control unit.
 3. The method according to claim 1, wherein the temperature within said storage area is controlled to a temperature in a range of 1° C. to 15° C.
 4. The method according to claim 1, wherein the aluminium alloy sheet material is made from an alloy selected from one of the AA registered alloys 6005, 6111, 6013, 6014, 6016, 6022,
 6056. 5. The method according to claim 1, wherein each individual coil within the set of coils is covered with a packaging.
 6. The method according to claim 5, wherein the packaging, is tightly wrapped around the individual coil.
 7. The method according to claim 5, wherein the packaging material comprises an anti-humidity material.
 8. The method according to claim 5, wherein the sides of each individual coil facing the sheet edges are fully covered with a protective material against abrasion.
 9. The method according to claim 5, wherein each individual coil within the set of coils is covered with a volatile corrosion inhibitor comprising packaging material.
 10. The method according to claim 1, wherein the housing within the storage area comprises at least one module of an anti-humidity material.
 11. The method according to claim 1, wherein the set of multiple coils of aluminium alloy sheet material has a number of coils in a range of 2 to
 20. 12. The method according to claim 1, wherein the set of multiple coils of aluminium alloy sheet material are stored for at least 30 days within said housing.
 13. A method of using an intermodal container having a housing defining a storage area adapted and configured to receive and store multiple coils of aluminium alloy sheet material, comprising storing and transporting said multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition in the intermodal container, wherein the housing comprises a temperature control unit integrated with said housing and operative to control the temperature within said storage area to a temperature in a range of 18° C. or less.
 14. Kit-of-parts formed by a set of multiple coils of 6xxx-series aluminium alloy sheet material in a T4 or T4P condition and an intermodal container having a housing defining a storage area adapted and configured to receive and store and transporting said coils, the housing comprises a temperature control unit integrated with said housing and operative to control the temperature within said storage area to a temperature in a range of 18° C. or less, for storing and transporting said set of multiple coils.
 15. The method according to claim 1, wherein the temperature within said storage area is controlled to temperature in a range of 15° C. or less.
 16. The method according to claim 1, wherein the temperature within said storage area is controlled to temperature in a range of 8° C. to 15° C.
 17. The method according to claim 6, wherein the packaging is a plastic foil.
 18. The method according to claim 5, wherein the packaging material comprises an anti-humidity material, inside the packaging material.
 19. The method according to claim 1, wherein the set of multiple coils of aluminium alloy sheet material are stored for at least 60 days within said housing.
 20. The method of use according to claim 13, wherein the temperature control unit integrated with said housing is operative to control the temperature within said storage area to temperature in a range of 15° C. or less, for storing and transporting the set of multiple coils of 6xxx-series aluminium alloy sheet material in T4 or T4P condition.
 21. The Kit-of-parts of claim 14, wherein the housing temperature control unit integrated with said housing is operative to control the temperature within said storage area to a temperature in a range of 15° C. or less, for storing and transporting the set of multiple coils in T4 or T4P condition. 